So, i have a rock n play. . I have been told it is a must! I think it's adorable and cant wait to try it for daytime use with a nap perhaps. BUT.. i have concerns about using this overnight and am hesitant to try that.. i may just use the crib right away for overnight. After doing some research i learned that too much time in a rock n play CAN cause flat head in babies.. has anyone else heard of this and is also concerned about too much time spent in a rock n play ???